The Diagnostic Medical/Behavioral Core will provide a framework for the identification and neurobehavioral screening evaluation of subjects entering into the individual projects. Before the state-of-the-art experimental procedures outlined in Core C and in the Projects can be applied to the study populations, it is crucial to determine whether individual children meet the neurologic and behavioral criteria for the group to which they are assigned. In addition, the Core neurologic and behavioral information provides a framework in which to better understand the significance of the experimental behavioral data. The major responsibilities of the Neurobehavioral Core B are: 1. Identification and induction of experimental and control subjects. 2. Screening of subjects for selection criteria as defined for each research project. 3. Administration and analysis of medical and behavioral questionnaires and medical/neurologic examinations. 4. Administration and scoring of a standardized behavioral test battery to all experimental and control subjects. 5. Tracking of all subjects from entry to completion of testing. 6. Acquisition of MRI sans when appropriate, with clinical interpretations performed by a clinical neuroradiologist. 7. Collaboration with Project Investigators to relate these diagnostic findings to the experimental findings obtained in the Project studies.